The general utility of pallets is well known for their use as a loading platform for storage and movement of products in quantity. Pallets provide a stable base for a manufacturer or distributor of a product to stack items thereon allowing for ease of movement by use of a forklift or pallet jack. Pallets are constructed from wood, metal, or plastic, and designed to be placed under materials that are to be shipped or stored, providing a clearance underneath for placement of a forklift or pallet jack.
Pallets are reusable requiring that they be durable in construction, lightweight, and stackable. Ideally, the pallet should occupy a minimum amount of space, both vertically and horizontally. The durability of a pallet is dependent on the type of material used for construction. Pallets constructed of wood will provide years of service if not exposed to harsh conditions that could cause rotting, or unusual loading situations which could cause collapse of the wood frame or wood components. Wood pallets are in constant need of repair wherein a damaged pallet slat is replaced with a new slat by either nailing or stapling to the base frame. A additional problem with wooden pallets is that wood is a porous material. When used in the food industry, wood can harbor bacterial growth which may contaminate food products. Relatedly, insects and other pests can burrow into the wood and be transported into and infest a previously uncontaminated storage area. Such pests can continue to reproduce and thrive in the wooden structure of the pallet.
Additionally, the porosity of the wood allows for absorption of water. Should the pallet freeze, it can be easily cracked when loaded, even when supporting lightweight products. Should a pallet absorb water, the weight of the pallet can cause difficulties in moving the pallet, and/or injuries to an individual manually moving the pallet. Moreover, splintering from the wood requires an individual who handles the pallet to wear gloves, and otherwise take precautions to prevent from injuring himself during relocation of the pallet.
Wooden pallets also have a significant disadvantage in that they do not interlock or readily stack. Accordingly, should a number of wooden pallets be placed on top of each other, the possibility exists for the pallets to tip over. The is particularly true when any of the pallets within the stack slips away from a squarely stacked position above the underlying pallet.
An alternative to wooden pallets includes metal pallets, such as those formed by aluminum. Metal pallets are known for their durability under normal circumstances. However, aluminum pallets are expensive to manufacture and once damaged, cannot be readily repaired. Should any interim damage occur, such as breach of a weldment, the pallet could have a catastrophic failure under a loaded condition. This could cause injury to operating personnel or damage to the materials positioned on the pallet.
Yet another material used for the construction of pallets is plastic. Plastic is capable of being sterilized, and is impervious to most environmental conditions. However, a plastic pallet is even more difficult to repair than metal if it is not modularly constructed. Should a portion of the pallet become damaged, the entire pallet is destroyed.
U.S. Pat. No. 5,197,395 ('395) discloses a plastic pallet. However, the top and bottom surfaces of '395 comprise a unitary, and not a modular, structure. Hence if the top or bottom unitary structures are damaged, the entire top or bottom structure, or even the whole pallet, must be replaced. The cost of such replacement makes the use of plastic pallets, as a direct replacement for wood pallets, cost prohibitive.
Moreover, despite their superior strength over wood pallets, plastic pallets still cannot withstand unusually forceful abuse, such as when a forklift or semi-truck runs over a portion of the pallet. In particular, the '395 patent subjects the internal locking means to load stresses. Such forces may cause the unitary plastic pallet to crack, whereas a wood pallet may only need a section replaced.
U.S. Pat. No. 5,483,899 ('899) discloses a pallet structure wherein the internal locking means are integrally formed with the vertical dimensioning means. As a result, this pallet puts forceful loads directly on the locking means which is likely to cause breakage under stress. Since the locking means is integrally formed with the pallet part, breakage would require replacement of the entire pallet part. Such breakage of the interconnecting means can prove to be extremely dangerous in that the whole pallet my thereby fall apart and spill heavy objects off of the pallet onto nearby persons.
Accordingly, what is lacking in the art is a lightweight, re-usable plastic pallet comprised of component parts that allows for modular construction and related ease of component replacement, and which avoids placing undue load stresses on interconnecting component parts which might fail under such stresses.